gitlab 看起来应该没问题，但事实并非如此——页面总是返回：
502 Whoops, GitLab is taking too much time to respond.
地位：
$ gitlab-ctl status
run: gitlab-workhorse: (pid 10244) 718s; run: log: (pid 6421) 2922s
run: logrotate: (pid 10252) 717s; run: log: (pid 6541) 2920s
run: nginx: (pid 10258) 717s; run: log: (pid 6422) 2922s
run: postgresql: (pid 10270) 716s; run: log: (pid 6486) 2921s
run: redis: (pid 10282) 716s; run: log: (pid 6420) 2922s
run: sidekiq: (pid 20207) 6s; run: log: (pid 6426) 2922s
run: unicorn: (pid 20224) 1s; run: log: (pid 6484) 2921s
Tail 反复显示以下几行：
$ gitlab-ctl tail
==> /var/log/gitlab/unicorn/current <==
2015-12-29_15:16:53.75860 master failed to start, check stderr log for details
2015-12-29_15:16:54.76660 failed to start a new unicorn master
2015-12-29_15:16:54.77909 starting new unicorn master
==> /var/log/gitlab/unicorn/unicorn_stderr.log <==
I, [2015-12-29T16:16:55.903009 #20344] INFO -- : Refreshing Gem list
==> /var/log/gitlab/unicorn/current <==
2015-12-29_15:17:01.52470 master failed to start, check stderr log for details
2015-12-29_15:17:02.53403 failed to start a new unicorn master
2015-12-29_15:17:02.55003 starting new unicorn master
==> /var/log/gitlab/unicorn/unicorn_stderr.log <==
I, [2015-12-29T16:17:03.876169 #20426] INFO -- : Refreshing Gem list
我知道这还不够，但我不知道如何让独角兽告诉我它出了什么问题:)
有什么建议吗，如何进一步调试？